The present invention relates to throwing machines and, in particular, an accurate object throwing machine having multiple axes that are controlled by a computer system to throw an object from a predefined release point with a predefined initial velocity, a predefined initial trajectory, and two predefined components of rotational motion.
Professional baseball, through attendance fees, broadcast rights, and various marketing activities, generates enormous annual revenues. However, because of the high salaries paid to professional baseball players and the high cost of stadiums and training facilities, baseball is a business of relatively close margins. In order to maintain and increase revenues from game attendance and from televised broadcasts, it is vital to maintain high levels of interest and excitement of baseball fans. Although low-scoring pitching duels may be the delight of baseball connoisseurs, fans are generally most interested and excited in games that feature relatively large numbers of base hits and home runs.
Successfully hitting a baseball pitched by a professional baseball pitcher is considered by many to be the single most difficult task undertaken by an athlete in professional sports. The speed of a pitched baseball, as it crosses home plate, may vary from between 60 and 70 mph to over 90 mph. The baseball may be released from any point within a relatively large area, depending on the height and stance of a pitcher and the type of pitch that is being thrown. A thrown baseball may exhibit any one of a large number of different, aerodynamically induced trajectories that depend on the orientation of the seams of the baseball with respect to the translational and rotational motions of the baseball, the initial velocity of the baseball, and the orientation of the rotational motion of the baseball with respect to the translational motion of the baseball. Because of the short travel time of a thrown baseball between the release point and home plate, on the order of between 4 and 5 tenths of a second, because of the relatively slow response times of a batter following the visual perception of the release and initial trajectory of a pitched baseball, and because of the large number of different, aerodynamically induced trajectories that a thrown baseball may follow, a batter has only milliseconds in which to either estimate the height and orientation with which a thrown baseball transverses a volume of space above home plate known as the strike zone and begin to swing the bat to meet the baseball or to conclude that the trajectory of the baseball will not intersect the strike zone and decline to swing the bat. Advances or delays of as little as 5 milliseconds in the timing of the initiation of the swing that would, if correctly timed, result in a home run, may result in a foul ball to the left-hand side of the field or a foul ball to the right-hand side of the field. Slight dislocations of the point of contact between the bat and the pitched baseball from the optimal point of contact can result in erratic pop-ups or foul balls.
Because fan enthusiasm depends, to a large extent, on the ability of batters to hit pitched baseballs, and because hitting pitched baseballs requires hand-eye coordination skills close to the limit of human ability, training of professional baseball players to consistently hit baseballs pitched by professional baseball pitchers is a vital and difficult component of a professional baseball training program. One effective approach to train batters to hit professional pitched baseballs would be to expose the batter to professional pitchers for many hours each day. However, the ability to pitch baseballs accurately, at high speeds, and with varying trajectories, is also a rare skill. In addition, pitching baseballs at the highest skill levels is an extremely physically demanding undertaking. Because of the high salaries paid to professional baseball pitchers, because of the relatively short duration in which a baseball pitcher can pitch baseballs at high skill levels without incurring an injury, and because of the relatively large number of pitches that need to be thrown to each batter in order to train that batter, it is impractical to use professional baseball pitchers to train batters.
As an alternative to using professional baseball pitchers, baseball teams may employ semi-professional or amateur pitchers for practice sessions. However, using semi-professional or amateur pitchers may also be expensive, and, most importantly, semi-professional and amateur pitchers cannot throw the baseball with the speeds, accuracies, and varying trajectories with which professional pitchers pitch the baseballs during games. For these reasons, baseball teams have employed a number of different pitching machines for repetitive batting practice.
Various types of pitching machines have been designed, manufactured and proposed. In one type of pitching machine, shown in FIG. 1, a baseball 102 is tethered by a line or cable 104 to a vertical rotating shaft 106 spun by an electric motor 108. The ball travels in a circular path within a horizontal plane, each revolution representing a pitch. In general, such devices poorly simulate a thrown baseball because the circular trajectory of the ball does not resemble the trajectory of a pitched baseball.
A large variety of different devices for projecting a baseball have been employed. Such devices may be placed at roughly the same distance from a practicing batter as the distance between a batter and the normal release point of a baseball pitcher. A number of different propulsion mechanisms have been used in these projecting devices, including pneumatic propulsion, electromagnetic acceleration, and spring driven lever arms. Although far better than the pitching machine displayed in FIG. 1, these various types of projecting pitching machines have also proved inadequate. In general, they are not able to faithfully replicate the motion of a baseball as thrown by a baseball pitcher. Furthermore, these devices are generally quite inaccurate, as well as unsafe due to the risk of injury to the batter. While a professional baseball pitcher can routinely pitch a baseball through the front face of the strike zone, a cube less than two feet on a side, the pitching machines pitch with much greater variation. As a result, a batter practicing against such machines naturally tends to adopt a more careful and hesitant attitude than the batter would adopt against a human pitcher. More problematic, these pitching machines generally pitch baseballs at slower speeds than a professional baseball pitcher, and generally do not pitch real baseballs. Pitching of real baseballs is problematic because the currently-available machines have no way of orienting the seams of the baseball and, without such orientation, the trajectory of the baseball becomes quite erratic because of aerodynamic affects,.
A far more successful type of pitching machine, produced by a number of pitching machine manufacturers, including The Jugs(trademark) Company, employs two counter-rotating rubber-tired wheels to propel a baseball towards a batter as well as to impart a rotational spin on the baseball. FIG. 2 illustrates a Jugs-type pitching machine. A human operator 202 places a baseball 204 into a mechanical feeder (not shown) through which the baseball rolls into a narrow space between the two counter-rotating rubber pneumatic tire and wheel assemblies that include wheels 206 and 208. The counter-rotating wheels 206 and 208 are independently driven by electric motors 210 and 212. The counter-rotating wheels rotate at speeds up to 3,000 rpm. The ball is briefly pinched between the wheels and then expelled at speeds that can approach 90 mph. By adjusting the rate of spin of one wheel with respect to the other, so that the two counter-rotating wheels rotate at slightly different speeds, a ball can be expelled from the device with a rotation, either forward or backward, in the plane in which the two counter-rotating wheels lie. Moreover, as shown in FIG. 3, the plane of the counter-rotating wheels can be tilted in order to alter the trajectory of the ball. In FIG. 3, for example, the ball follows a curved path between the Jugs machine and the batter because of a tilted spin imparted to the ball by the tilted counter-rotating wheels. The Jugs machine can be adjusted along a number of different axes. For example, the mechanism may be rotated with respect to a vertical axis in order to adjust the initial horizontal trajectory of the pitched ball. The assembly can be vertically adjusted about a horizontal axis to vary the angle at which a ball is pitched with relation to the ground. These vertical and horizontal adjustments together describe the initial translational trajectory of the baseball. Because the counter-rotating wheels are driven by separate electrical motors, their relative rotational speeds can be adjusted to impart different degrees of spin in both the forward and backward directions to the ball.
While a vast improvement over the previously described devices, the Jugs machine nonetheless falls far short of the capabilities of a human baseball pitcher. First, the Jugs machine does not accurately pitch real baseballs because the Jugs machine cannot orient the seams of a real baseball reliably, and thus cannot control the aerodynamically induced motion of the baseball. Instead, a dimpled plastic ball is normally used. Second, there are additional rotational motions that can be imparted to the baseball by a human pitcher that the Jugs machine cannot reproduce. The Jugs machine does not have enough controllable axes in order to reproduce a human thrown baseball. Finally, the Jugs machine does not reproduce the visual appearance of a human baseball pitcher, including varying release points for varying pitches. The release point can be adjusted on a Jugs machine by raising and lowering the counter-rotating wheel assembly, but this operation requires a rather lengthy period of time and a rather lengthy period of recalibration.
In order to simulate a live human pitcher, manufacturers have attempted to combine projection of a video image of a baseball pitcher with baseball pitching machines of various types, most commonly, a Jugs-type baseball pitching machine. FIG. 4 illustrates a live-motion, video-image pitching machine system. A live-motion image of a baseball pitcher 402 is projected onto a screen 404. At the point in time at which the image of the baseball pitcher releases the baseball, a baseball is ejected from a small stationary port 406 in the plane of the projection screen 404. In general, these systems have been rather crudely implemented and do not reproduce the timing and appearance of a human pitcher. First, as with the other above mentioned pitching machines, these systems generally do not pitch real baseballs, but instead pitch dimpled plastic baseballs, with the same lack of ability to reproduce the actual motion of pitched baseballs as inherent in all the above described pitching machines. Moreover, the release point 406 is fixed on the screen, whereas a human pitcher releases the balls at varying locations on a release-point plane at various distances from the batter, depending on the different types of pitches that are being thrown and on the physical characteristics of the pitcher. Finally, all of these systems place the projection screen closer to the batter than the 60-foot distance that normally separates a batter from a human pitcher, generally from as little as 20 feet up to a maximum of 50 feet. To make up for the shortened distance, the ball is thrown at slower speeds. However, the visual effect produced by these systems is much different that the visual effect produced by a human pitcher throwing at normal speeds and by the aerodynamic motion of a pitched baseball.
Because of the increasingly thin profit margins in the baseball business, the need for improving professional baseball batting is becomingly increasingly important. Currently available baseball pitching machines cannot closely reproduce the motions of baseballs pitched by human pitchers. Currently available baseball pitching systems cannot reproduce the visual appearance of a human pitcher, nor can they reproduce the varying release points and the motions of human pitched baseballs. For these reasons, a need has been recognized for a baseball pitching machine that can faithfully reproduce the motions and trajectories of pitched baseballs and that can faithfully reproduce the appearance of a human pitcher. In addition, for many of the above-described reasons, object projecting machines configured to repeatedly and faithfully reproduce thrown and batted objects are equally desirable for simulating other aspects of baseball and other types of sports, including tennis, hockey, martial arts, football, ping-pong, and badminton, and may have additional industrial applications.
One embodiment of the present invention is a multi-axis, servo-controlled baseball pitching machine (xe2x80x9cBPMxe2x80x9d). A full-motion image of a baseball pitcher is displayed on a vertical projection screen at the front of the BPM. The moving image of the baseball pitcher simulates the positions and movements of a baseball pitcher. Various moving images can simulate a variety of different types of pitches pitched by any number of different baseball pitchers. At the point in time that the baseball is released from the simulated pitcher""s hand, a physical baseball is projected through the projection screen, from the position of the release point of the baseball portrayed in the projected image, towards a defined position relative to a human batter. Thus, the BPM of one embodiment of the present invention visually simulates the position and motions of various baseball pitchers throwing different types of pitches and projects a baseball towards the batter with a predetermined initial speed and with a predefined trajectory that faithfully reproduces the type of pitch being thrown by the simulated baseball pitcher.
The BPM features a dynamic release point, or port, that can be positioned anywhere within a large portion of the projection screen in order to coincide in time and position with the release of the baseball by the simulated pitcher. The dynamic port operates as a shutter that is opened for a very short period of time to allow a baseball to pass through the projection screen. The action of the shutter is not visible to the batter, since it is actuated in less than {fraction (1/25)}th of a second, below the visual acuity threshold for humans.
The baseball is gripped by a gripper component and horizontally translated between two cylindrically shaped counter-rotating flywheels. The cylindrical surface of the two flywheels is coated with a compressible material that grips the baseball through frictional forces. The rotational momentum of the counter-rotating flywheels is then instantaneously imparted to the baseball when the gripper component forces the baseball between the two counter-rotating flywheels and projects it at a high speed towards home plate in the direction of a horizontal axis between the two counter rotating flywheels. The speed of the ball is controlled by the rotational speed of the counter-rotating flywheels, each driven by an electrical servo motor. A rotational spin either in a clockwise or a counterclockwise direction in a plane passing through and bisecting both counter-rotating flywheels can be imparted to the baseball by rotating the two counter-rotating flywheels at different speeds. The angle of the spin with respect to the vertical can be adjusted by rotating both flywheels about a projection axis passing between the two flywheels, orthogonal to a line segment between the centers of the two flywheels and coplanar with the plane passing through and bisecting both counter-rotating flywheels, along which the baseball is initially projected. When rotation of the flywheels about the projection axis occurs at the time that the baseball is projected from between the flywheels, an additional spin can be imparted to the baseball in a plane orthogonal to the projection axis passing between the two flywheels.
The flywheels and the servo motors driving the flywheels are mounted in an assembly that can be horizontally and vertically translated with respect to the projection screen, thus placing the release point of the baseball at any point within in a planar area coincident with, and bounded by, the plane of the projection screen. In addition, the assembly can be driven by additional servo motors to rotate about a pivot in the horizontal direction and to rotate about a pivot in the vertical direction in order to orient the projection axis within an imaginary cone perpendicular to the projection screen and opening out and away from the projection screen from the release point of the baseball in the direction of projection of the baseball.
The reflective surface of the projection screen comprises five flexible sheets. A first flexible sheet is attached to the left side of the assembly in which the counter-rotating flywheels are mounted and is taken up by a vertically-mounted, spring-loaded take-up reel on the left side of the baseball machine. Similarly, a second flexible reflective sheet is attached to the right side of the assembly in which the flywheels are mounted and is taken up by a vertically mounted, spring-loaded take-up reel on the right side of the baseball machine. A third reflective, flexible sheet with a slot, or aperture, is held between lower and upper horizontally-mounted, electrical servo operated reels that are positioned below and above the assembly in which the flywheels are mounted and that are translated horizontally with respect to the projection screen along with the assembly in which the flywheels are mounted. By moving the aperture in the third flexible sheet to a location coincident with the projection axis at the time that the baseball is projected between the two flywheels, a small, shutter-like opening briefly appears in the surface of the projection screen in order to allow the baseball to pass through the projection screen. A fourth flexible sheet is attached to the top of the assembly in which the counter-rotating flywheels are mounted and is taken up by a horizontally-mounted, spring-loaded take-up reel on the top of the baseball machine. Similarly, a fifth flexible reflective sheet is attached to the bottom of the assembly in which the flywheels are mounted and is taken up by a horizontally mounted, spring-loaded take-up reel on the bottom of the baseball machine. The fourth and fifth flexible sheets lie behind the third flexible sheet so that the aperture in the third sheet cannot be moved in front of exposed, open spaces above and below the assembly in which the flywheels are mounted.
The speeds of the two counter-rotating flywheels, the release point of the baseball, the initial direction at which the baseball is projected away from the projection screen, and the angle of the plane bisecting the two counter-rotating flywheels with respect to the projection axis can all be controlled and adjusted by computer control of electrical servo motors to faithfully reproduce the trajectories of various types of baseball pitches, including the fastball, the curveball, the knuckleball, and the slider. Moreover, the various types of pitches can be coordinated with the projected images of a baseball pitcher to simulate pitching of the baseball by any number of different baseball pitchers. Finally, the trajectory with which the baseball passes through the strike zone can be accurately predetermined by computer control of the electrical servo motors to within a radius of two inches from a desired trajectory when the baseball is projected from a distance of 60 feet.
Modification of certain components of the object projection machine of the present invention can be made to produce a tennis ball serving machine, a martial arts weapons throwing machine, a football passing machine, and other types of sports simulators. The object projection machine may also find use in industrial simulators, test equipment, and mass conveyance devices.